Tiny microbes could make New Zealand's drinking water safer

Some drinking water in New Zealand, especially in rural areas like Canterbury, has more nitrate than is considered safe.

High nitrate levels can be dangerous for babies and may affect people’s health over time, according to the country’s largest nitrate survey and the Government’s 'Our Environment 2025' report.

Associate Professor Wei-Qin Zhuang and his team from the Department of Civil and Environmental Engineering are tackling this problem using tiny microbes (natural water cleaning 'bugs') to remove nitrate safely, without adding harmful chemicals.

Zhuang says his team are testing two approaches.

• Hydrogen-powered microbes: These bacteria use hydrogen gas as fuel to turn nitrate into harmless nitrogen gas, which makes up most of the air we breathe. This process avoids the greenhouse-gas emissions that can come from conventional chemical treatments. The hydrogen is delivered safely so it never bubbles out, keeping the process clean and simple.
  
  
• Sulfur-powered microbes: Other bacteria 'eat' sulfur like tiny Pac-Men, using it to remove nitrate. Packed into a filter-like setup, this system works steadily without daily chemical dosing, making it low-cost and easy to run for small towns and rural water supplies.
  

Zhuang says both systems create less waste, avoid greenhouse-gas-intensive chemicals, and reduce the need for trucked-in chemicals, making them well suited to local communities.

"Many rural water supplies have nitrate levels at or above the safe limit, and people using private wells often don’t know if their water is safe," he says.

"Using microbes to clean water on-site gives communities a safety net while long-term solutions, like better land management, are put in place."

Zhuang and his team are now testing these systems in real-world trials with water utilities and industry partners, aiming to make them easy for councils and communities across New Zealand to use.